The present invention relates to a novel and useful apparatus for non-invasively identifying components associated with a liquid within a container.
Chemical entities are often stored and transported in a liquid medium by containers and conduits. For example, medical solutions such as enteral, parenteral, and other nutrients are compounded or mixed in an intravenous bag fed by separate tubes leading from pure sources of material. In particular, 70% dextrose injection U.S.P., 10% Travasol (amino acid injection), Intralipid 20% I.V. Lipid emulsion, sterile water, potassium chloride, and the like are combined in this manner. Many systems have been proposed to determine the identity of components associated with a liquid passing through a tube or lying in a container using electrical characteristics of the particular component within the tube. For example, such systems are generally invasive, in that the particular probe or electrode of a probe contacts the fluid within the container or tube. Invasive measurements of this type are not acceptable in certain applications such as medical fluids which are intravenously delivered to a patient.
For example, U.S. Pat. No. 3,774,238 describes an invasive measurement of pipeline material utilizing three capacitors to determine dielectric properties of the material.
U.S. Pat. No. 4,074,184 employs invasive capacitance measurements of non-conductive fluids in a tube to determine the vapor-liquid phase ratio.
U.S. Pat. No. 4,227,151 shows an invasive measuring cell for use in determining the electrical conductivity of fluids in a container.
U.S. Pat. No. 4,924,702 describes invasive capacitance sensors that determine the liquid level of a container.
U.S. Pat. No. 4,928,065 shows an invasive measuring apparatus which provides an electrical field from electrodes to determine the characteristics of non-aqueous low conductivity suspensions.
U.S. Pat. No. 4,935,207 employs an invasive capacitive sensor which detects analyte ions in a liquid container.
U.S. Pat. No. 5,068,617 teaches an invasive capacitive device which measures the mixing ratios of composite liquids within a container.
U.S. Pat. No. 5,208,544 describes an invasive sensor which produces dielectric measurements on high temperature molten polymer compositions flowing in a conduit.
U.S. Pat. No. 5,255,656 delineates an electronic sensor which invasively measures the methanol-gasoline mixture in a fuel line by the use of capacitive elements.
U.S. Pat. No. 5,266,899 discloses an invasive salt analyzer which measures the conductivity of saline solutions by inductive non-contact.
U.S. Pat. No. 5,296,843 shows a fluid or vapor diagnostic device employing an invasive probe which generates a light beam passed through a container to a detector to determine the vapor-liquid ratio within that container.
Several systems have been proposed which non-invasively determine the characteristics of fluid in a conduit or container. For example, U.S. Pat. No. 5,239,860 utilizes a light beam which is sent through a tube and detected after interaction with a gasoline alcohol mixture. The wavelength transmission characteristics then determine the actual alcohol-gasoline mixture within the tube.
U.S. Pat. No. 5,260,665 utilizes a non-invasive resonance cell with a pair of probes located therewithin to determine the presence of bubbles within the fluid line passing through the resonance cavity.
An apparatus which is capable of non-invasively identifying components in a container using the electrical conductivity characteristics of the fluid therewithin would be a notable advance in the medical field.